1. Technical Field
This invention relates to an at least partially implantable system for rehabilitation of a hearing disorder with an arrangement for processing and/or generating signals, which includes an implantable processor arrangement with control logic which operates according to an operating program and an implantable memory arrangement for storage of the operating program and of operating parameters. Also, the invention relates to systems including a wireless telemetry means for data transmission between the implantable part of the system and an external unit, and a power supply arrangement which supplies individual components of the system with current.
2. Description of Related Art
Rehabilitation of sensory hearing disorders with partially implantable electronic systems in recent years has acquired major importance. The expression "hearing disorder" is defined here as inner ear damage, middle ear damage, combined inner ear and middle ear damage, cochlear deafness which necessitates use of a cochlea implant, likewise retrocochlear hearing disorders which necessitate use of an auditory brain stem implant, i.e. briefly, everything which prevents or adversely affects sound reception and/or relay to the brain stem. "Hearing disorders" here furthermore include temporary or permanent noise in the ears (tinnitus). In particular, the use of partially implantable electronic systems applies to the group of patients in which hearing has completely failed due to accident, illness or other effects or is congenitally absent. If, in these cases, only the inner ear (cochlea), and not the neuronal auditory path which leads to the center, is affected, the remaining auditory nerve can be stimulated with electrical stimulation signals and thus a hearing impression can be produced which can lead to clear understanding of speech. In these so-called cochlea implants, an array of stimulation electrodes, which is triggered by an electronic system, is inserted into the cochlea. This hermetically tight and biocompatibly encapsulated electronic module is surgically embedded in the bony area behind the ear (mastoid). However, the electronic system contains essentially only decoder and driver circuits for the stimulating electrodes, sound reception and conversion of this acoustic signal into electrical signals, while their further processing takes place basically externally in a so-called speech processor which is carried outside on the body. The speech processor converts the preprocessing signals coded accordingly into a high frequency carrier signal which via inductive coupling is transmitted through the closed skin (transcutaneously) to the implant. The sound-receiving microphone is located without exception outside the body, and in most applications, in a housing of a behind-the-ear hearing aid worn on the external ear, and is connected to the speech processor by a cable. These cochlea implant systems, their components and principles of transcutaneous signal transmission are described by way of example in U.S. Pat. No. 5,070,535, U.S. Pat. No. 4,441,210, published European patent application No. 0 200 321 and U.S. Pat. No. 5,626,629. Methods of speech processing and coding in cochlea implants are disclosed for example, in published European patent No. 0 823 188, published European patent No. 0 190 836, U.S. Pat. No. 5,597,380, U.S. Pat. No. 5,271,397, U.S. Pat. No. 5,095,904, U.S. Pat. No. 5,601,617 and U.S. Pat. No. 5,603,726.
In addition to the rehabilitation of deaf patients, or those who have lost their hearing, using cochlea implants, for some time there have been approaches to offer better rehabilitation using partially or fully implantable hearing aids than with conventional hearing aids to patients with sensorineural hearing disorder which cannot be surgically corrected. The principle consists, in most embodiments, in directly stimulating an ossicle of the middle ear or the inner ear via mechanical or hydromechanical stimulation and not via the amplified acoustic signal of a conventional hearing aid in which the amplified acoustic signal is sent to the external auditory canal. The actuator stimulus of these electromechanical systems is accomplished with different physical transducer principles such as, for example, by electromagnetic and piezoelectric systems. The advantage of these processes lies mainly in the sound quality which is improved compared to conventional hearing aids and, for fully implanted systems, in the fact that the hearing prosthesis is not visible. These partially and fully implantable electromechanical hearing aids are described, for example, by Yanigahara et al. in Arch Otolaryngol Head Neck, Surg-Vol 113, August 1987, pp. 869-872; Suzuki et al. in Advances in Audiology, Vol. 4, Karger Basel, 1988; Leysieffer et al. in HNO, Vol. 46, 1998, pp. 853-863; Zenner et al. in HNO, Vol. 46, 1998, pp. 844-852; and in numerous patent documents, especially in commonly assigned U.S. patent application Ser. No. 09/097,710, in U.S. Pat. Nos. 4,850,962; 5,277,694; 5,411,467; 5,814,095; 3,764,748; 4,352,960; 5,015,224; 5,015,225; 3,557,775; 3,712,962; 4,729,366; 4,998,333; and 5,859,916, published European Patent No. 0 263 254, published PCT Application Nos. 98/36711; 98/06237; 98/03035; 99/08481; 99/08475; 99/07436; and 97/18689.
Many patients with inner ear damage also suffer from temporary or permanent noise in the ears (tinnitus) which cannot be surgically corrected and against which there are no drug forms of treatment to date. Therefore, so-called tinnitus maskers are available; they are small, battery-driven devices which are worn like a hearing aid behind or in the ear. By means of artificial sounds which are emitted via, for example, a hearing aid speaker into the auditory canal, the maskers mask the tinnitus by psychoacoustic means and thus reduce the disturbing noise in the ears, as much as possible, below the threshold of perception. The artificial sounds are often narrowband noise (for example, third-octave noise) which can be adjusted in its spectral location and loudness level via a programming device to enable adaptation to the individual tinnitus situation as optimally as possible. In addition, recently, the so-called retraining method has been introduced in which by combination of a mental training program and presenting broadband sound (noise) near the resting hearing threshold, the perceptibility of the tinnitus is likewise to be largely suppressed Journal "Hoerakustik" 2/97, pages 26 and 27). The devices used in this training program are also called "noisers".
In the two aforementioned methods for hardware treatment of tinnitus, hearing aid-like technical devices must be worn visibly outside on the body in the area of the ear. These devices stigmatize the wearer and therefore are not willingly worn.
U.S. Pat. No. 5,795,287 discloses an implantable tinnitus masker with direct drive of the middle ear, for example, via an electromechanical converter, coupled to the ossicular chain. This directly coupled transducer can preferably be a so-called "Floating Mass Transducer" (FMT). This FMT corresponds to the transducer for implantable hearing aids which is described in U.S. Pat. No. 5,624,376.
Implantable systems for the treatment of tinnitus by masking and/or noiser functions have been proposed, in which corresponding electronic modules are added to the signal-processing electronic path of a partially or fully implantable hearing system such that the signals necessary for tinnitus masking or noiser functions can be fed into the signal processing path of the hearing aid function and the pertinent signal parameters can be adapted by further electronic measures individually to the pathological requirements. This adaptability can be accomplished by the necessary setting data of the signal generation and feed electronics being filed or programmed in the same physical and logic data storage area of the implant system. Also, the feed of the masker or noiser signal into the audio path of the hearing implant can be controlled via the corresponding electronic means.
In all the above-described rehabilitation devices, it now seems to be a good idea to design the systems such that they can be completely implanted. These hearing systems, depending on the desired function, consist of three or four function units: a sensor (microphone) which converts the incident airborne sound into an electrical signal; an electronic signal processing, amplification and implant control unit; an electromechanical or implantable electroacoustic transducer which converts the amplified and preprocessed sensor signals into mechanical or acoustic vibrations and sends the signals, via suitable coupling mechanisms, to the damaged middle and/or inner ear, or a cochlear stimulation electrode for cochlea implants; and an electric power supply system which supplies the aforementioned modules. Furthermore, there can be an external unit which makes available electrical recharging energy to the implant when the implant-side power supply unit contains a rechargeable (secondary) battery. Especially advantageous devices and processes for charging of rechargeable implant batteries are described in commonly assigned U.S. patent application Ser. No. 09/311,566 and in published European patent No. 0 499 939. Feasibly, a telemetry unit can also be provided with which patient-specific, audiological data can be transmitted bidirectionally or programmed in the implant and thus permanently stored, as was described by Leysieffer et al. in HNO Vol. 46, 1998, pp. 853-863.
Basically, in all the above-described at least partially implantable systems, the (audio) signal processing or signal generation and the modules of the implant control are built, for example, like a controlled battery recharging system or a telemetry system for bidirectional transmission of, for example, variable, patient-specific parameters on the implant-side by permanently fixed hardware units. This design feature also applies in cases in which digital signal processors or microcontrollers or microprocessors are used for signal processing or generation or for implant management, regardless of whether they are built as so-called "hardwired logic", i.e. in "hardwired" logic architecture, or whether their operating programs are filed in the read-only memories (ROM) of the corresponding processors. These programs, which are provided and necessary for basic operation of the implant and for proper operation, are called hereinafter the operating program or operating software. This operating software is placed in the implant systems described in the prior art during production, for example, by mask programming of the processor storage areas and can no longer be changed after implantation.
In contrast, patient-specific data such as, for example, audiologic adaptation data or also variable implant system parameters (for example, as a variable in one of the aforementioned software programs for controlling battery recharging) are referred to as operating parameters. These operating parameters can be transmitted transcutaneously to the implant according to the aforementioned prior art in fully implantable implant systems after implantation, i.e. wirelessly through the closed skin and, thus, can be changed.
If, on the other hand, the operating software is to be changed because, for example, due to more recent scientific findings, improved algorithms for speech signal processing are available in, for example, fully implanted cochlea implants or electromechanical hearing systems for rehabilitation of an inner ear disorder, the entire implant or implant module which contains the corresponding signal processing unit must be replaced by a new unit containing the altered operating software by invasive surgery on the patient. This surgery entails renewed medical risks for the patient, and is especially serious in the application of cochlea implants in children as patients. In addition, the surgery is very costly. In addition, this system change can only be done completely, especially in cochlea implants, i.e. with removal of the stimulation electrode, since a technically very complex, multipin and detachable plug connection to the signal processing implant module is not used given the currently conventional large number of stimulus channels.